During this study, each group was assigned a year; 2003, 2005, 2006, 2008, 2009 or 2011 for which they were provided with LANDSAT 5 imagery to determine impervious surface percentages for each watershed. This was accomplished through a remote sensing computer program called ERDAS. Remote sensing is using satellite imagery, which includes readings from sensors beyond the abilities of human perception, to interpret different factors such as land cover, land use change, vegetation, and soil cover.

With remote sensing the satellite images are classed and counted as a percentage of total land. For example 20% of a given area is forested. These percentages are multiplied by the impervious quotient as defined by the Atlanta Regional Commission and in use by the Georgia Adopt-A-Stream. Different land cover receives different impervious quotients; forest generally is 5% impervious while major roads have an impervious quotient much higher at 90% impervious. The resulting numbers are the percentages for a given land cover’s impervious surface in proportion to its percent of land cover within the watershed. So if 20% of a watershed is forest: 20% X .005 = .2% impervious surfaces contributed by forests. Once these final percentages are calculated for all classes of land use, they are summed and this is your total impervious surface for each watershed.

The point of conducting this remote sensing was to detect change in impervious surfaces and contrast this to possible factors of poor water quality.